Monitoring of trimethoprim antibiotic residue in livestock and marine products commercialized in Korea

A survey for trimethoprim (TMP) was performed using 369 livestock and marine products distributed in Korea. Product samples included beef, pork, milk, egg, chicken, flatfish, jacopever, common eel, and shrimp. TMP residues were analyzed using ultra performance LC with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). The analytical method was validated according to FDA (U.S. Food and Drug Administration) guidelines and all results fully complied with FDA recommendations. TMP was detected in 7 product samples (1.9% incidence), including 5 jacopever, 1 flatfish, and 1 common eel. Residue levels were 1.17 to 16.43 μg/kg in jacopever, 40.0 μg/kg in flatfish, and 13.3 μg/kg in common eel. All positive product samples were below the legal residue limit of 20- 50 μg/kg in the Korean food code.